1. Field of the Invention
This invention relates generally to polymerization emulsifiers and, more specifically, to polymerization emulsifiers comprising surface-active tertiary alkylamines, obtainable by reacting long-chain epoxides with diethanolamine, followed by ethoxylation and, if desired, by salt formation or quaternization.
2. Statement of the Related Art
It is known that the polymerization of ethylenically unsaturated monomers substantially insoluble in water can be carried out in aqueous dispersion in the presence of emulsifiers. A large number of such emulsifiers, predominantly anionic, but also cationic and nonionic, have been described. One particularly important class of emulsifiers are the nonionic adducts of long-chain compounds and ethylene oxide.
Numerous nitrogen-containing polymerization emulsifiers are also known, such as the fatty amine salts proposed in pamphlet number HOE 4200 of Hoechst AG (West Germany). However, fatty amine salts lose their surface-active properties at basic pH-values, which is a disadvantage for many applications in the emulsion polymerization field. Ethoxylated fatty amines having a degree of ethoxylation below 10 have the same disadvantage. Other known polymerization emulsifiers include ethoxylated fatty acid amides produced by the amidation of fatty acid esters with ethanolamine or diethanolamine, followed by ethoxylation. Products of this type are described, for example, in German patent application No. 23 33 417. The disadvantage of these and similar products lies in the hydrolyzability of the amide function which can lead to a gradual loss of surface activity through hydrolysis. Adducts of ethylene oxide and/or propylene oxide with aliphatic diamines are also known and described, for example, in U.S. Pat. No. 2,979,528. Unfortunately, these adducts are not biodegradable.
Those skilled in the art are not able to predict with accuracy from the chemical structure the suitability of a given compound for use in emulsion polymerization. Accordingly, in view of the many requirements which polymer dispersions now must satisfy, there is a continuing need for new polymerization emulsifiers and, more especially, for new N-containing polymerization emulsifiers. In particular, there are applications which require emulsifiers capable of changing their surface-active properties through changes in pH.